The present invention relates to automatic power circuit breaker accessories and particularly to a universal packaging arrangement for the various types of accessory devices commonly utilized in power circuit breakers.
As electrical power distribution systems become more sophisticated, increasing demands are being placed on power circuit breakers to perform collateral functions in addition to their primay function of circuit protection. To this end, circuit breakers are equipped with a wide variety of accessory devices to accommodate these collateral functions. Thus, shunt trips are installed in power circuit breakers to accommodate tripping of the breaker from a remote location initiated manually or automatically in response to a condition not necessarily related to the currents flowing in the breaker poles. Accessory switches are installed in power circuit breakers to sense when the breaker is closed or open, and if open, whether it was manually opened or tripped open. The contacts of these accessory switches are wired into external circuits to effect indicating and control functions. To protect loads such as motors from possible damage due to low line voltage, circuit breakers are equipped with undervoltage releases (UVR) to trip the breaker in response to prolong low line voltage conditions.
In many installations, circuit breakers may be equipped with not one, but several of these accessory device. Particularly in the case of molded case power circuit breakers, the space available to accommodate these accessory devices is at a premium. Moreover, in the close confines of a molded circuit breaker case, isolating the accessory devices from live breaker parts is a signficant problem. For these reasons, plus the fact that the accessories are typically of different sizes and shapes calling for unique mounting provisions, circuit breaker accessories have traditionally been factory installed items. Thus installation of these accessory devices to add their collateral functions to circuit breakers in the field is typically not convenient and, in many instances, not UL approved.
It is accordingly an object of the present invention to provide a family of improved circuit breaker accessory devices.
A further object is to provide accessory devices of the above character wherein each accessory type is packaged in a standardized manner to greatly simplify their installation in power circuit breakers, both in the factory and in the field.
Yet another object is to provide accessory devices of the above character wherein each accessory type is packaged in a standardized insulative, molded case.
An additional object is to provide a family of molded case accessory devices of the above character which are uniformly compact in size, economical to fabricate and assemble, and reliable in operation.
Other objects of the invention will in part be obvious and in part appear hereinafter.